I wouldn't think too much into it. From my experience (literally only 5 days) some girls put kisses on the end of text when they are going out with you for example my ex, but they don't put kisses on texts any other time and some girls for example my friend puts kisses on all texts for no reason what so ever. If you're not going out then it's probably a case of the latter. But I don't text enough girls to say for sure.